A gas turbine engine generally includes a fan and a core arranged in flow communication with one another. Additionally, the core of the gas turbine engine generally includes, in serial flow order, a compressor section, a combustion section, a turbine section, and an exhaust section. In operation, an airflow is provided from the fan to an inlet of the compressor section where one or more axial compressors progressively compress the air until it reaches the combustion section. Fuel is mixed with the compressed air and burned within the combustion section to provide combustion gases. The combustion gases are routed from the combustion section to the turbine section. The flow of combustion gases through the turbine section drives the compressor section and is then routed through the exhaust section, e.g., to atmosphere. In particular configurations, the turbine section is mechanically coupled to the compressor section by one or more shafts extending along an axial direction of the gas turbine engine.
The fan includes a plurality of blades having a radius larger than the core of the gas turbine engine. The fan and plurality of blades may also be mechanically coupled to one of the one or more shafts such that they rotate along with the turbine. Rotation of the plurality of blades generates thrust for the gas turbine engine and provides airflow to the compressor section of the core.
For at least some gas turbine engines, the fan is a variable pitch fan. It can be desirable to vary a pitch of the fan blades by rotating the blades about respective pitch axes to further increase performance of the gas turbine engine. For example, a primary reason for changing blade pitch is to adjust the blade's angle of attack for optimal performance based on the present air speed of the aircraft and power level of the engine. Alternatively, the pitch of fan blades may be used to reverse the airflow, bypassing the core of the engine, thus providing reverse thrust to aerodynamically brake a landing aircraft.
An actuation member is typically provided in operable communication with the plurality of fan blades to change the pitch of the plurality of fan blades. The actuation member may be powered by, e.g., a hydraulic or electric system. If, however, the power system of the actuation member fails, it may be possible for the plurality of fan blades to rotate from a pitch range for generating forward thrust to a pitch range for generating reverse thrust. If such takes place during forward flight, damage may occur.
Accordingly, an actuation member having one or more safety mechanisms in place to prevent the plurality of fan blades from rotating from a pitch range for generating forward thrust to a pitch range for generating reverse thrust in the event of a system failure would be useful. More particularly, an actuation member having one or more safety mechanisms in place to prevent the plurality of fan blades from rotating from a pitch range for generating forward thrust to a pitch range for generating reverse thrust that can prevent such rotation independent of the power system of the actuation member would be particularly beneficial.